1. Field of the Invention
The invention relates generally to broadcast television systems and more particularly to a system and method for booking events and initiating actions in response to detecting these events in a broadcast television receiver.
2. Description of Related Art
It is useful in computer systems to be able to detect particular events and to initiate particular actions in response to these events. For example, in desktop computer systems, it may be desirable to display an email icon when an email message is received. The computer system may also be configured to launch a specific application at a particular time. Similar mechanisms may also be found in videocassette recorders (VCRs), which are typically configured to be able to schedule the recording of a particular channel when an internal clock reaches a predetermined time. A VCR may also be configured to begin recording a channel when it receives specific information (e.g., information indicating the start of a particular television program) transmitted in the analog vertical blanking interval (VBI) of a broadcast signal. In television systems proposed by the Advanced Television Enhancement Forum (ATVEF), a trigger in a television broadcast signal can cause the television receiver to display a particular HTML page.
The systems described above, however, have limitations which prevent them from being extended to a generalized event booking mechanism in a broadcast television receiver. For example, in the case of email notifiers and calendar services on desktop computer systems, the events which can be detected and the actions which can be initiated in response thereto are specifically defined for particular applications (e.g., an email application displays an icon in response to receiving a new email message.) The applications provide internal mechanisms which cannot be used by other applications. If a different application requires an additional type of event to be detected or an additional type of action to be initiated, that application must typically provide its own mechanism for detecting that type in event and initiating the respective action. Because this type of mechanism has statically defined events and actions, and requires additional application code (as well as additional memory to store the code), it is not suitable for the limited resources of a broadcast television receiver. Mechanisms which use triggers (such as VBI or ATVEF triggers) that are delivered in a broadcast signal suffer from these same limitations. These triggers detect statically defined events and initiate statically defined actions. Further, if the action includes launching an application, the application must be present. That is, it cannot be downloaded upon detection of the event and then launched. Consequently, these mechanisms are not suitable for a generalized event booking system in a broadcast television receiver.